Sometimes when I read a post, it's kinda confusing to see when the post is finished (and the signature start), although there is a line between them. It's most often when there are some quotes in the post (which contains lines too).
So, my suggestion, would it be possible to make the signature 'less' visible, I mean you could for example make the signature grey in stead of black.
And I'm sure there will be other solutions too (e.g. italic).